eight pinnate tentacles and the same 

 number of mesenteries or partitions. All 

 are marine and the great majority form 

 colonies which assume arborescent or 

 tree-like forms. The growth of these 

 masses is very iiiteresting, but difficult to 

 understand from the dried specimens 

 usually seen in our museums. When 

 alive each branch or coral stock is com- 

 posed of soft, fleshy tissue, called the coe- 

 nenchyma, throughout which there rami- 

 fies hundreds of little irregular canals 

 which serve to connect the polyps with 

 each other. Scattered over the surface 

 of this fleshy foundation are many little 

 cylindrical Coral animals (polyps), the 

 distal end of which is surmounted by 

 eight pinnate tentacles which surround 

 the oval mouth. The outer skin, called 

 sarcosome, forms a calyx or cup into 

 which each polyp may be withdrawn 

 and completely concealed when dis- 

 turbed. The coenenchyma, as well as 

 the polyp itself, is more or less sup- 

 ported by numerous calcareous spicules, 

 which may be scattered throughout the 

 mass or may form a regular skeletal sup- 

 port, as in the hard part of the precious 

 Coral and the fan-like structure of the 

 sea fans. In one family there is a horny 

 secretion which covers the polyp. The 

 alcyonarian polyps increase in size by a 

 system of budding from the sides or 

 top of the Coral stock. The fleshy stock 

 or foundation pushes forward its rami- 

 fying canals, which carry nutritive mate- 

 rial, and at the base of an old polyp or 

 on disk-like expansions new polyps be- 

 gin to grow or bud out, much as do the 

 buds of a flower. By constant budding 

 in this manner a large Coral stock may 

 be built up. These animals have no spe- 

 cial outlet for the waste products of di- 

 gestion. These are thrown out of the 

 mouth when all nutritive matter has been 

 extracted. 



The lowest forms belong to the order 

 Alcyonacea which includes many corals 

 supported by a fleshy coral stock. In 

 many cases these animals encrust foreign 

 objects. The most familiar member of 

 this order is the organ coral (Tubipora 

 musica). This coral is common through- 

 out the Indian and Pacific Oceans, and 

 the coral stock often attains an immense 

 size. Each coral polyp forms a red tube 



and each series of polyps is separated 

 from the series below by a horizontal 

 partition, so that in a large specimen 

 of this coral stock there seems to be a. 

 number of tiers of tubes, each tier being 

 separated from the one above and below 

 by a flat partition or floor. It is this pe- 

 culiar form which has given it the name 

 of organ coral. Each little polyp is able 

 to retract into its tube and thus secure 

 protection from its enemies. 



In the order Pennatulacea or sea- 

 pens and sea-feathers, the coral polyps 

 form upon a stock called the rachis. 

 This bears a stalk which is embedded in 

 the mud or sand. The colonies are more 

 or less locomotive and are able to move 

 from place to place. One of the most 

 striking forms of this order is the Re- 

 nilla, the rachis of which is spread out 

 in the form of a leaf or a kidney. A 

 long pedicel or stem extends from the 

 lower surface and anchors the colony to 

 some foreign object by means of a pe- 

 culiar polyp-like organ called a siphon- 

 ozoid, or siphon-animal. The upper sur- 

 face of the rachis is covered with many 

 little coral polyps which are attached to 

 the rachis by a rather long stem. The 

 tentacles are wide and covered with lit- 

 tle feather-like expansions on the edges. 

 The rachis is of a rich purple color, the 

 polyps being of a much lighter shade. 

 According to Agassiz these animals are 

 remarkably phosphorescent, emitting "a 

 golden green light of a most wonderful 

 softness." They are found in the Gulf 

 of Mexico and in the Atlantic and Paci- 

 fic Oceans. Many of the sea-pens form 

 a long, feather-like rachis, not a few of 

 which live in very deep water. 



Another order is the Gorgoniacea 

 which includes the large and showy sea- 

 fans and sea-plumes. They are all at- 

 tached to some solid base and the axis 

 or coral stock is more or less firm and 

 is covered by a fieshy coenechyma. The 

 coral polyps project from this fleshy cov- 

 ering and when their tentacles are ex- 

 panded they resemble many little stars. 

 The best known members of this order 

 are found in the family Gorgoniidae. The 

 common Gorgonia flabellum or sea-fan 

 is a most beautiful object, the vertical 

 and lateral extensions of the coral stock 

 forming an exquisite lattice work. In 



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